Interest in the role of public opinion in foreign policy has grown steadily since the end of the Second World War. We distinguish at least three different waves of research on this topic and examine two main components of the present policy debate: the need for an Atlantic community and agreement on the means to reach common goals. As to the first issue, we explore the extent to which Atlanticism—defined as the willingness to cooperate among European partners and the US on problems perceived as common—is still high in the 2000s. We find considerable variation between European countries and the US. The left-right cleavage is still relevant in explaining attitudes toward collaboration across the Atlantic both in the US and in several European countries. As to the means, we look at the issue of support for the use of military force in Europe and the United States. On the basis of the available data, support for the use of force is much higher, across the board, in the US than in Europe. On the other hand, the contextual conditions under which force will be used seem to make a significant difference, albeit in different ways, in Europe and the US.